DE 20 2005 017 237 U1 discloses a tank filling system, the protective cap of which is screwable onto a pouring spout. The protective cap has a venting position in which the protective cap is not completely sealed off with respect to the pouring spout and so the container can be vented and a differential pressure between the container interior and the atmosphere can be equalized.
U.S. Pat. No. 5,406,994 discloses a canister having a pouring spout which has a valve. In the unactuated state of the pouring spout, the valve is closed. The valve is opened when the pouring spout is pushed onto the filler neck of a container to be filled. In this case, a venting valve of the pouring spout is also opened.